Styrofoam is widely used as an insulation material for buildings due to excellent productivity and thermal insulation, light weight and affordable price. However, according to environment-friendly policies for energy saving and low-carbon emission, styrofoam with improved thermal insulation property and flame retardancy is required both domestically and internationally. Improvement in thermal insulation of styrofoam may not only achieve energy saving and reduce density and thickness of styrofoam to involve a less amount of styrofoam, contributing to a decrease in manufacture costs, but also increase a living space. Accordingly, various attempts are made to enhance thermal insulation property of styrofoam, for example, 1) a method of preparing expandable polystyrene particles in which graphite or a material for enhancing thermal insulation property is dispersed by adding graphite or the material for enhancing thermal insulation property in polymerization of expandable polystyrene, 2) a method of preparing expandable polystyrene particles in which graphite or material for enhancing thermal insulation property is dispersed by thermally melting polystyrene and injecting and extruding graphite, the material for enhancing thermal insulation property and a foaming agent, and 3) a method of preparing expandable polystyrene particles which a material for enhancing thermal insulation property is infiltrated into and applied to by infiltrating and applying the material for enhancing thermal insulation property to a surface layer of the expandable polystyrene particles using an organic solvent.
However, the foregoing methods may achieve thermal insulation improving effects but involve complicated manufacture processes, lowered cost efficiency in equipment and manufacture costs and difficulty in obtaining satisfactory fusion property, compressive strength and flexural breaking load in molding.